Engine Room (Forward)
The "fire room," which comprised the forward end of the engine room, lay
immediately aft of the boilers. Here crew tended the Monitor's boilers
and controlled the main engine. Both required considerable maintenance. Crew
members continually fed the boiler fires and tended the coals, while engineers
and sailors monitored the various pressure and temperature gauges on an hourly
basis.

As on the berth deck,
all lighting in the engineering areas was
artificial, and the iron walls bore white paint to reflect what little light
there was. In good weather, one could open the crew's hatch in the overhead,
but the area mostly remained sealed so the blowers could efficiently fan the
furnace fires.

Aft of the boilers was the Monitor's main engine. Another original
conception of the ship's inventor John Ericsson, the engine was not unique in
design but it was unique for then-modern naval warships. The vibrating
side-lever engine had one main cylinder that housed two pistons operating on a
horizontal plane instead of the more traditional vertical plane. On each side
of the engine lay a "rock shaft," which a short arm connected to the piston
trunk. At the aft end of the rock shafts, arms attached to the propeller shaft
via connecting rods. As the pistons slid back and forth, the rocking motion
translated into rotation at the propeller shaft.

The vibrating side-lever engine allowed rotation of the propeller shaft to be
applied at a 90-degree angle to the main cylinder, while the horizontal design
of the cylinders enabled Ericsson to place all of the machinery low in the hull
below waterline and behind the Monitor's protective armor.

At the back of the engine was the valve chest. This area was "operation
central" for the main machinery. Using a series of levers, cranks, and wheels,
the men worked the vibrating side-lever engine at the captain's whim.

Below the valve chest lay two of the Monitor's bilge pumps. These pumps
were rated at 2,500 gallons per minute, more than capable of keeping the bilges
dry. Ericsson also equipped the ship with a centrifugal bilge pump that was
rated at over 3,500 gallons per minute. The blower drive pumps were mounted
floor-to-ceiling at the outboard sides of the fire room. The small steam
engines drove the large blowers with thick leather belts.

The engine itself stood on a raised platform, which crew members accessed via a
set of stairs on the starboard side. From this area, sailors had access to all
of the main engine's moving parts. Vigilance was essential during operation of
the main engine. The engineering crew had to ensure all moving parts were
sufficiently lubricated for peak performance. A damaged piece of machinery
could take weeks to replace, as most of the parts would have to be
fabricated.